EoW March 2012

Technical article

This is due to the higher maintenance and replacement cost of XLPE cable as compared to that of TR-XLPE cable because the life-cycle of XLPE cable is shorter than TR-XLPE cable, even though XLPE cable costs 5% less than TR-XLPE cable initially. Conclusion Until testing standards are specified for distribution power cables, stakeholders across the value chain should take it upon themselves to be aware and make decisions that will ultimately deliver long-term value and reliability. Specifiers should become familiar with a variety of materials that are proven to offer the benefits needed by their companies and their consumers. Testing facilities, cable manufacturers and materials suppliers should work more closely to make this information easy to understand and to access. Ultimately, there may be global standards that will further encourage this kind of partnership and teamwork that will benefit the entire industry as well as the consumers of energy. n

Poor quality equipment, even though having a lower initial cost, can lead to higher maintenance (such as repeated failures) and replacement cost, due to shorter than expected life-cycle. Use of either water barriers or TR-XLPE materials in cable design will increase the cost of finished cables. The additional cost of cables must be justified via rigorous financial analysis. LCC has been applied recently by utilities to evaluate the procurement of new equipment. Although the initial cost of TR-XLPE cables is estimated to be slightly higher than XLPE cables, LCC analysis demonstrates that the value of TR-XLPE cables far exceeds the initial cost increment over XLPE cables, due to the significant cost savings achieved with a longer performance life and higher reliability. A model has been created to compare the LCC of XLPE and TR-XLPE cables, using the various cost inputs as shown in Table 3 . Initial cable cost was estimated based on copper price of US$9,500/MT. TR-XLPE cable was assumed to cost 5% more than standard XLPE cable, based on differences in price of XLPE and TR-XLPE materials. Number of cable failures prior to total cable replacement (between joints) can be adjusted. Installation cost of replacement cables can also be adjusted as needed. The failure cost shown only accounted for the repair cost of the cable failure and did not include loss of revenue. However, additional cost associated with power loss due to cable failures can be included in the model. To enhance the accuracy of computation, more than two life-cycles are used in the LCC analysis. For example, consider the situation after 75 years – the XLPE-insulated cable will have been replaced twice whereas the TR-XLPE insulated cable will only have been replaced once. The model computes the net-present-value (NPV) of total cost of each cable. Tabulated in Table 4 is the computed total cost difference of XLPE and TR-XLPE cables of various life-cycles. For example, when comparing a XLPE cable with a life-cycle of 30 years and a TR-XLPE cable with a life-cycle of 40 years, the LCC difference between them is USD$64,965/km, meaning the LCC of the XLPE cable is $64,965/km more than the TR-XLPE cable.

Dow Electrical and Telecommunications – USA Email : info@dow.com Website : www.dow.com

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EuroWire – March 2012